When U.S. Secretary of Homeland Security Janet Napolitano spoke at the NYU School of Law on June 7 at the invitation of the Brennan Center for Justice, she observed that her talk fell between “two focusing events”: the death of Osama bin Laden and the 10th anniversary of 9/11.

In a sweeping speech, “Strength, Security, and Shared Responsibility: Preventing Terrorist Attacks a Decade After 9/11,” Napolitano discussed the many responsibilities and challenges tackled by the Department of Homeland Security, which, with more than 200,000 employees, is the third-largest cabinet department. Although her talk focused primarily on counterterrorism, she reminded the audience that Homeland Security also oversees border security, immigration enforcement, cybersecurity, and natural-disaster response.

While she said the U.S. was stronger than it was on or just before 9/11 and had learned many important lessons, the terrorism threat was still real and evolving. The most important fact to convey, she said, was that the federal government alone could not protect the country without the help of states, local law enforcement, first responders, the private sector, and individual Americans: “Everyone has a stake in the safety of our people.”

Among the areas Napolitano stressed were the assimilation and sharing of information among key homeland security players; the need to understand the current trend toward smaller, harder-to-detect terrorist plots, which are with increasing frequency hatched by Americans rather than outsiders; and the futility of policing beliefs or profiling based on religion or ethnicity. She also emphasized two key ideas: national security begins with local security, and if citizens see something unusual, they should say something about it. Napolitano freely gave credit to the “If you see something, say something” campaign promoted by New York City’s Metropolitan Transit Authority for the latter concept.

Despite the nation’s security needs, she said, “There is a false dichotomy if you say we have to sacrifice liberty for security. We don’t. We just have to think about them at the same time and look for common-sense and pragmatic ways to make sure that both are being pursued.”

Napolitano focused near the end of her speech on the public’s role in protecting America. Between 1999 and 2010, she said, individual citizens helped stop a third of foiled domestic terrorist plots, while most of the others were halted not just through federal efforts, but with the aid of state and local law enforcement: “What we’re talking about is making sure that, across this country, every single person is incorporating and understanding the role they play.”

She emphasized the ongoing nature of the efforts required for successful homeland security: “We need as a country to keep adapting, to think ahead, to be nimble and to be adaptive as individuals, as communities, and as a nation. We have made great strides, but, even given that, we cannot provide guarantees. And while all the things I’ve discussed with you today are steps forward, we will never put this country under a kind of glass dome and seal it against all threats.... We have to, on the one hand, be proactive and thoughtful, thinking always what could be around the next corner. And on the other hand, have confidence that we have built in our communities the ability to respond and to respond quickly, to come back. And it’s with that kind of confidence that we proceed.”